The present invention relates to gas turbine engines, and more particularly, to an actuator for varying the position of guide vanes in a gas turbine engine.
Gas turbine engines may be used to power various types of flight vehicles, both manned and unmanned. The basic principles and operation of gas turbine engines are generally well understood. Air is funneled into an inlet of the engine where it is compressed and ignited causing the air and fuel to rapidly expand. The rapid expansion provides energy to propel the engine either by thrust or a combination of thrust and a rotating fan (e.g., as in a turbofan engine).
As a simplistic example, a gas turbine engine may include four major sections, a compressor section, a combustor section, a turbine section, and an exhaust section. Air is funneled through an inlet into the compressor section where the compressor raises the pressure of the air it receives from the inlet. Depending on the application requirements, multiple compressors may be used to increase the pressure of the air as it moves through the compressor section.
The compressed air from the compressor section then enters the combustor section, where typically a ring of fuel nozzles injects a steady stream of fuel into the compressed air stream. The compressed air and fuel is then ignited by a burner causing rapid expansion. The expanding air from the combustor section flows through the turbine section causing rotationally mounted turbine blades to rotate and generate energy to drive the compressor section, among others. Again, the turbine section may include multiple stages to more efficiently extract energy from the airflow. The air exiting the turbine section is exhausted from the engine via the exhaust section, thereby creating thrust.
The output power of a gas turbine engine may be controlled by metering the fuel flow rate to the engine as well as the airflow into the engine. In particular, altering the airflow into the engine has a significant impact on the power and efficiency of the engine. In many applications, an engine controller monitors and controls the fuel delivery and airflow into the engine.
The airflow is typically adjusted by manipulating radial guide vanes near the inlet to the engine. For example, by altering the frontal area of inlet guide vanes and downstream stator vanes, the airflow into the engine can be varied between maximum and minimum airflow as needed depending upon the combustion conditions (e.g., air temperature, air density, engine load, and the like). By altering the frontal area of the vanes, the amount of air passing into the engine is controlled to optimize the combustion process given the current operating parameters.
Variable guide vanes, whether inlet guide vanes or stator vanes, are typically pivotally coupled to a unison ring, such that as the unison ring rotates, the guide vanes pivot uniformly. The guide vanes may be rotated between a closed position, in which airflow through the guide vanes and into the engine is substantially prevented, and an open position, in which airflow through guide vanes is substantially unrestricted. Additionally, the guide vanes may also be rotated to any number of orientations between the closed and open position, to more efficiently tune the combustion process.
Conventional gas turbine engines typically incorporate an electric motor or hydraulic system to actuate the adjustment of the variable vanes (e.g., inlet guide vanes, stator vanes, and the like). The motor(s) continue to move the actuators, unison ring, and thus guide vanes, until the guide vanes reach the position commanded by the controller. Position sensors supply position feedback signals representative of actuator position, and thus guide vane position, to the controller. When the position feedback signals indicate that guide vanes have reached the commanded position, the controller will de-energize the motor(s).
While these solutions may be appropriate for mainstream commercial aircraft operating at sub-sonic speeds below Mach 1 (i.e., approximately 761 miles per hour [1,024 kilometers per hour] at seal level at 59 degrees Fahrenheit [15 degrees Celsius]), the environment created by supersonic and hypersonic flight of manned or unmanned transport vehicles and missiles, or other air (or space) delivered weaponry, present significant new challenges to the actuation of turbine guide vanes. Typical solutions and designs are no longer applicable at these increased velocities. Additionally, other factors such as minimizing weight, controlling cost, extending range, and improving efficiency have an increased influence on the design.
To contextualize the extreme velocities in which the present invention can be suitably used, at 20,000 thousand feet above sea level, an aircraft traveling at Mach 5 is moving at approximately 3,500 miles per hour [approximately 5,600 kilometers per hour]—five times faster than an aircraft traveling at Mach 1 and approximately 55 times faster than an automobile on an interstate. At that rate, an aircraft could travel from New York, N.Y. to Los Angeles, Calif. in about 48 minutes. The extreme conditions cause materials to undergo considerable distortion that significantly complicates the design, construction, and operation of components of the aircraft.
This high rate of speed (i.e., near Mach 1 and faster) requires that the aircraft displace a considerable amount of air, which in turn, leads to a significant amount of friction, and thus, heat generated by the aircraft. Additionally, and especially at Mach 1 and greater, the aircraft locally compresses the air surrounding the aircraft, generating even more heat that is transferred to the components of the aircraft. An aircraft traveling at supersonic and hypersonic speeds can be operating at temperatures upwards of 1,200 degrees Fahrenheit [approximately 650 degrees Celsius].
In addition to the complications of extreme temperatures, significant vibrations and stresses are imparted to the aircraft at such high speeds (i.e., approaching Mach 1 and above). The amplitude and frequency of vibrations imparted to the components are more extreme than those imparted at sub-sonic speeds. Again, these vibrations and stresses are unique to the high speed environment and place increased demands on the design, construction, and operation of components of the aircraft.
Operating an aircraft, whether manned or unmanned, at supersonic and hypersonic speeds presents significant challenges in terms of the design, construction, and operation of the aircraft. Dynamic components used to control the operation of the engine, such as variable guide vane actuators, present an even more significant design challenge. Thus, a need exists for a variable guide vane actuator that is capable for use in the extreme environments of supersonic and hypersonic flight.